Devices for determining a penetration depth of a drill into a workpiece to be processed are widely used and known according to the prior art.
Such devices can be configured relatively simply, for example, in the form of a straightedge which is adjustable in length and is arranged parallel to the drill of the drilling machine.
Furthermore, devices for determining a penetration depth can also have a more complex configuration, as is explained below.
According to the prior art a device is known, for example, in which two laser light sources are positioned on a drilling machine at an angle relative to one another and emit two convergent light beams from the drilling machine in the direction of a workpiece surface. The two light beams are discernible as two circles of light on the workpiece surface. The two circles of light move towards one another on the workpiece surface when the drilling machine is moved in the direction of the workpiece surface. In this case the two laser light sources are adjustable relative to one another so that, when the two circles of light overlap, the user receives an indication of a specific distance of the drilling machine from the workpiece surface or a penetration depth of the drill into the workpiece. Such a device for determining a penetration depth is disclosed in the European patent document EP 1 464 428 B1.
Furthermore, a penetration depth determination device on a drilling machine is known according to the prior art, which device comprises a measuring unit with a light-emitting diode and a light sensor unit. In this case the light sensor unit contains two sensors. In this device a light beam is emitted by the light-emitting diode and is reflected by the workpiece surface. The light sensor serves for sensing light which is emitted by the light-emitting diode and is reflected by the workpiece surface. The ratio of the light intensities detected by the two sensors of the light sensor unit is determined by the angle of reflection of the sensed light component on the workpiece surface. The angle of reflection in turn is determined by the distance of the measuring unit or, respectively, the drilling machine from the workpiece surface. The penetration depth into the workpiece can be determined by the ascertained distance of the measuring unit or, respectively, the drilling machine from the workpiece. Such a device for determining a penetration depth is disclosed in the German patent application DE 10 2004 024 990 A1.
The devices described above for determining a penetration depth according to the prior art have relatively complex construction and handling. Because of this complexity, incorrect use of these devices can frequently occur. Furthermore, due to their complexity these devices are susceptible to malfunction, difficult to maintain and expensive.